This invention relates to a method and apparatus for connecting underwater conduits and, more specifically, to a method and apparatus which is capable of performing the diverless connection of underwater flowlinesxe2x80x94both flexible and rigidxe2x80x94in any combination of each other, and connection of the said flowlines to underwater structures such as flowline bases, xmas trees, templates or similar.
There are various recognised methods of diverless connection of underwater flowlines to underwater structures. The methods used for such connections are characterised mainly by two principal factors; the use of permanently installed underwater hardware known as a tie-in porch or reaction structures and the strict dependency upon the related connection system (connector). Both the permanently installed underwater hardware and connection system are critical parameters. The items of hardware required to support the connection operations are usually installed during flowline or underwater structure installation, any deviation from standard procedures required by the installers could result in a very high cost impact making the system less competitive than other alternative options. Furthermore, the strict dependence upon a given connection system can limit the use of the system to certain applications.
The above reasons highlight the need for an alternative method which is able to overcome both the needs of permanently installed underwater hardware and the dependence upon a given connection system whilst ensuring the same operating reliability as existing systems. In addition, the selection of an intervention philosophy requiring the use of neutrally buoyant tools optimises the flexibility of the presented method thus avoiding any dependency on the surface support vessel.
The aim of the present invention is to negate these drawbacks by providing a system which allows fully remote connection of underwater flowlines without using any permanently installed underwater hardware, allowing the use of any type of connection system, and performing all the operations using only the remotely operated vehicle to install and operate all the system""s tools.
According to one aspect of the present invention there is provided a method of connecting underwater conduits from a support vessel on the surface comprising the steps of launching a remotely operated vehicle from the support vessel, launching connection apparatus from the support vessel; manipulating the remotely operated vehicle to dock with the connecting apparatus; installing the connection apparatus to one of the conduits; activating a docking clamp means using the remotely operated vehicle to capture the end of the first conduit; activating the connection apparatus to draw the second conduit to the first; connecting the two conduits together to form a continuous flowline; providing a sealed connection, and recovering the remotely operated vehicle and connection apparatus to the support vessel.
Each of the above method steps are carried out without the need for underwater personnel. Each step is monitored and controlled from the support vessel thereby increasing the efficiency and safety of the connection process.
Additionally, the method includes the step of supporting the conduit on a frame above the sea bed.
Advantageously, the remotely operated vehicle carries out a survey of the work site and sends a report to the support vessel prior to connection of the conduits
According to the further aspect of the present invention there is provided an apparatus for connecting underwater conduits being controlled from a support vessel on the surface, the apparatus comprising a remotely controlled vehicle launchable and recoverable from the support vessel; connection apparatus launchable and recoverable from the support vessel; means for docking the remotely operated vehicle to the connection apparatus; means for mounting the connection apparatus on one or both of the conduits; means provided for capturing the end of the other conduit and drawing the second conduit to the first to enable a connection of the conduits to form a continuous flow line; means to effect the connection and means for providing a sealed joint.
Advantageously, each of the connection apparatus is launched in a sledge from the support vessel.
Preferably, a support frame is also launched from the support vessel, the support frame being placed around one or both (depending on the field layout) of the conduits by the remotely operated vehicle to raise the conduit from the sea bed.
Advantageously, the frame is a light-weight metallic frame substantially H-shape in configuration.
Preferably an interface skid is provided which is connected to the remotely controlled vehicle, launchable and recoverable from the support vessel, which allows the remotely controlled vehicle to dock mechanically, hydraulically and electrically to the connecting apparatus in order to provide power for the connecting apparatus.
Conveniently, an interface collar is provided on the free end of the flexible conduits to allow the connection apparatus to be mounted in position on the flexible conduits.
Advantageously, buoyancy modules are provided in addition to the support frame. These modules act along with the support frame thereby raising the conduit from the seabed to enable connection of the adjacent conduit to be carried out.
Conveniently, the support frame and the connection apparatus are substantially buoyant in water to enable manoeuvrability by means of the remotely operated vehicle.
Advantageously, the manipulation means on the remotely operated vehicle is an articulated arm having a closeable grab arrangement at the free end thereof